Exhaust gas of conventional diesel vehicles includes carbon monoxide, hydrocarbons, and nitrogen oxides as harmful materials. Nitrogen oxides cause environmental problems such as photochemical smog and acid rain, as well as human diseases. Therefore, there is a demand for improving engines and developing a post-treatment technology of exhaust gas.
One of the most effective technologies for removing nitrogen oxides uses a selective catalytic reduction (SCR) method. This method has been developed according to a reducing agent such as ammonia (NH3), urea, hydrocarbon (HC), and the like, and various catalysts. Ammonia (NH3) has been known to be effective in removing nitrogen oxides from a fixed object such as a power plant and an incinerator. Since there is a problem of storage/transport and use of ammonia, in case of a moving object such as a vehicle, urea has been known to be effective as it is capable of being easily decomposed to ammonia by heat decomposition and a hydration reaction.
As the catalyst for use in the selective catalyst reduction method, zeolite-based catalysts such as copper(Cu)/zeolite having excellent functions has been developed.
In particular, high temperature activity of such a catalyst is very important in treatment of high-temperature exhaust gas.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.